The semiconductor industry has experienced rapid growth due to improvements in the integration density of a variety of electronic components (e.g., transistors, diodes, resistors, capacitors, etc.). For the most part, this improvement in integration density has come from shrinking the semiconductor process node (e.g., shrink the process node towards the sub-20 nm node). As semiconductor devices are scaled down, new techniques are needed to maintain the electronic components' performance from one generation to the next. Device complexity is increasing as manufacturers design smaller feature sizes and more functionality into integrated circuits. Such complex devices may result in more lithography steps.
As semiconductor technologies evolve, advanced lithography techniques have been widely used in today's integrated circuit fabrication processes. Photolithographic techniques involves forming a photoresist layer over a substrate, exposing portions of the photoresist material to a pattern of light in accordance with a desired pattern, developing the photoresist material to remove portions of the photoresist material to expose portions of the underlying material. A suitable etching process such as dry etching, wet etching and/or the like may then be performed on the substrate. As a result, the exposed underlying material may be removed in accordance with the desired pattern.
The exposure step of the lithography process may involve a variety of reticles (a.k.a. photo masks). Each reticle is a quartz plate having transparent and opaque regions. The transparent and opaque regions replicate a pattern representing an integrated circuit component on the surface of a wafer. The lithography process of the integrated circuit may comprise multiple photolithography process steps due to the complexity of the manufacturing process. Each lithography step may employ a reticle through which the pattern of a component of an integrated circuit is generated.
An integrated circuit fab may comprise a variety of lithography apparatuses such as steppers, immersion scanners and the like. In addition, the fab may have a plurality of stockers for storing wafers and reticles. The factory is automated by using automatic guided vehicles to transport wafers and reticles and using robots to load wafers and reticles into lithography apparatuses.
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the various embodiments and are not necessarily drawn to scale.